chargers

[Andrew Cousins]

Guys been reading through the threads on this topic(chargers) and picked up some information but its getting a bit clouded. Could any body give me a straight answer as possible to my following questions.

I fly IC both my son and myself, We have one Transmitter at the moment which we use to fly a trainer and another low wing improver plane. We are using 4.8 volt 2200mah batteries in the RX for both planes and for the TX as well. I am looking to switch to a 6V 2200mah battery for the transmitter so we can get more flights out of the TX.

Question with these various batteries would it be a good investment to get a charger discharge to keep the batteries in good condition or is it a waist of money and just stick to the charger that came with the transmitter.

I have no intensions at this moment in time to go electric flight if this helps.

Many Thanks

Andy C

[..]

Andy , I see no reason for you to need to change from your standard trickle charge that came with the set originally.

Others may differ in opinion but for your needs I would stay as you are , it's all I use for the 14 planes & 2 transmitters I have in use.

[Geoff S]

Personally, I would never use a wall wart trickle charger except when I had absolutely no alternative. There are loads of very inexpensive chargers around that will give you an indication of just how much energy you've stored into your batteries and will also give you an idea of the battery's health.

I'm also doubtful that changing from a 4.8v battery to a 6v one in your transmitter will extend the amount of time you can use it. The higher voltage will merely cause the built-in regulator to work harder and throw away the extra energy in heat. A better way to extend use time would be to buy a second 4.8v pack and change it at the field as the other becomes depleted.

Geoff

[Wes]

The wall charger will work fine, but there are cheap chargers out there which would only charge the batteries the amount they need, whereas its usual practice to have the wall charger on all night.

And as Geoff suggests, they help you keep an eye on the condition of the battery.

The idea of changing from 4.8 to 6v for the TX seems a bit alien, it's more usual to have either Nimh or Lipo as a choice for the TX. A higher capacity battery would give you longer life.

It may help advice if you specified the TX you have, also I would have thought the RX battery would be the limiting factor rather than the TX battery.

[Peter Christy]

Andy, You don't say what transmitter you are using, which makes it a bit difficult to advise, but the fact that it is running off 4.8 volts indicates that it is probably a 2.4 GHz set of some kind.

Most transmitters draw somewhere between 100 and 200mA in use (ignoring top of the range types, with illuminated lcd screens!) Assuming 200 mA consumption, that should give you 10 hours operation between charges, with a 10% safety margin. Even if you double the consumption rate and knock a bit more off for safety, you should be good for 4 hours continuous operation from a full charge.

Nearly all 2.4 GHz gear operates at or around 5 volts internally, and will have a voltage regulator to reduce any excess voltage to this level. If you increase your transmitter voltage to 6 volts, it will still draw more or less the same current - ie, no increase in operating time! The extra voltage will simply be dissipated as heat in the regulator.

If you need to increase the operating time, you need to increase the the mAH rating of the batteries. Alternatively, you could get a fast peak-detect type charger and top it up off the car battery (or whatever) while you have a break. But in any case, most of us have difficulty in managing an hour of use on a typical flying day, so I would have thought 4-5 hours operation - probably more - would be quite adequate!

Good quality NiMh cells do not need periodic cycling, unlike their NiCad predecessors. But I do recommend using a peak detect charger for charging them. If you only use, say, 20% of the charge on a days flying (not untypical) and then leave it on charge overnight at the 10 hour rate, you will be continually over-charging your battery. Although in the short term this will do no harm, it will dry out the electrolyte in the long term and shorten the life of the battery. Also, if done in a damp environment (shed or garage), continual over-charging can eventually lead to corrosion of the wiring looms - the dreaded "black-wire" corrosion.

A good peak detect charger, set to a 1 hour charge rate, will cut off as soon as the pack is fully charged and prolong the life of the pack. It will also minimise the risk (longer term) of black wire corrosion.

One caveat with peak detect chargers: Many transmitters now incorporate the charger circuitry into the Tx, with the "wall-wart" being a simple power supply. Do not try and use a peak detect charger through the existing socket on the Tx unless you know that it is a simple, direct connection to the battery!

It is possible that your transmitter already contains a peak detect charger, but without further information, it is impossible to say.

--

Pete

[iqon]

For what its worth i use the wall charger`s all the time, however - what if you forgot to turn one on and wanted to go flying. What would you do. ?

buy a B6 charger, does not have to be anything special any make will do. Will do nimhs and all the rest, but beware they dont all come with power leads, may have to buy that separately

[Andrew Cousins]

Guys many thanks for the information My TX is a futaba T8J. 2.4GHz

Basically I am trying to squeeze the maximum amount of flying time in using one TX with two planes. My sons trainer and my improver. Once my son has decided he wants to stay in the hobby I will buy him a TX but until then we will use my TX.

So I would be better getting a 4.8V eneloop 2500mah for the TX. Got a 2200mah Ni-MH at the moment.

The charger that I have is the Futaba dual output wall mount charger that will do 4.8v or 6 v batteries it also states that it is a peak detect. Is this charger any good?

[gangster]

Andy. Have you had any issues with battery capacity with that set up? I would have thought even with both of you flying you would be hard pressed to get that amount of flying in I am not sure increasing to 6 volts will increase duration at all. I am not sure a 5 cell AA will fit in there and you might need some shorter hump pack . There is no harm in buying a nice new 4.8 volt 2500 envelop for peace of mind but it may not give any or much more flying time than your 2200 There is nothing wrong with that pfc32d wall wart charger I have used one for over 3 years with the same 4.8 volt battery with no issues at all on a Futaba 8j

[Peter Christy]

Andy,

The charger you have is fine, and will not over-charge your batteries. You will not see any significant improvement by going from 2200 to 2500 batteries, nor will going to 6volt packs make any difference.

The packs you have should be good for several hours of continuous operation, and I would be amazed if you managed to run your transmitter flat on a typical day's flying.

I think you are worrying unnecessarily!

Cheers,

--

Pete

[Peter Christy]

P.S. If you are still worried, simply buy a second transmitter battery - same as the first - and charge that up too. Then, half way through the day, swap the packs over!

A modern external charger will show you how much your battery takes when being re-charged. One of your club-mates is bound to have one. After a good days flying, get him to charge it for you and tell you how much it takes. I think you will be amazed by how little you have used.

The manual for you transmitter doesn't specify current consumption (strangely!), but it does say that the original supplied batteries were only 1700 mAH, so 2200's should be more than adequate!

--

Pete

[..]

Posted by Andrew Cousins on 03/08/2016 11:37:03:

Guys many thanks for the information My TX is a futaba T8J. 2.4GHz

Basically I am trying to squeeze the maximum amount of flying time in using one TX with two planes. My sons trainer and my improver. Once my son has decided he wants to stay in the hobby I will buy him a TX but until then we will use my TX.

So I would be better getting a 4.8V eneloop 2500mah for the TX. Got a 2200mah Ni-MH at the moment.

The charger that I have is the Futaba dual output wall mount charger that will do 4.8v or 6 v batteries it also states that it is a peak detect. Is this charger any good?

Yes Andy it's all good , as suggested above and for your own piece of mind a spare pack would be an option? But as for charging etc at this stage keep it simple.

[Andrew Cousins]

Guys many thanks for all your information. I have learnt a lot Much appreciated.

Andy C

[Allan Bennett]

Mention has been made of peak-detect chargers but, in my experience, they are only really useful if you need to fast-charge a pack (if, that is, the pack is actually capable of taking a fast charge). What they do not do is ensure that each individual cell in the pack is fully charged -- they might end up with some cells over-charged and some under-charged, giving the correct total voltage for the whole pack.

The normal wall-wart charger that comes with the trannie usually charges the pack at a mA rate which is 1/10 or less of the pack's mAh capacity, for 12 to 14 hours. The idea of this is that the slow charge rate is low enough that it won't harm the cells if they reach their full charge before the charge is stopped, and the duration is long enough that it will ensure that every cell reaches full charge.

Sorry, don't know why the font size increased, nor how to change it back!

[gangster]

Some good points there Allen I believe that peak detect chargers can indeed be a bit of a pain at times and short of monitoring every cell,as we do on a lipo balance charge nothing can beat a good slow equalising charge. The good old fashioned basic charger is absolutely fine. I am sure people are quite often taken in by the sophistication of the more expensive chargers that lead them to turn up their noses at the basic chargers on the basis of sophisticated must be best. I also think that too much fast charging is done The wall wart supplied with the Futaba is somewhere between the two it is a 600mA peak detect. My thoughts as far as the op is concerned is to keep using the charger supplied by Futaba and recommended battery

[Peter Christy]

Allan / Gangster, yes, you are quite right that an overnight trickle charge will act as a "balancer" for NiXX cells. However, it shouldn't need to be done very often, unless you have very old cells. And modern "hybrid" cells, such as Eneloops, rarely need this, in my experience.

My point was that yes, the OP's charger is perfectly adequate for charging his cells. But he seemed to be worried that he didn't have enough capacity in his pack for sharing the Tx between two models. A good peak detect charger will tell him exactly how much charge he has used during a day's flying, and should reassure him that he has ample capacity. I'm sure one of his club-mates will have such a charger and be able to carry out this simple test for him, saving him the cost of buying one for himself.

Regarding "balancing" NiMh cells, yes trickle charging will do this. However, as I pointed out earlier, once a NiXX cell reaches a full charge, it will start to vent gas. Eventually this will dry out the electrolyte. It may take some time for this to reach a critical state, but a peak detect charger will prevent this.

Further, the vented gas appears to have a positive charge, and in a damp environment will combine with the water in the air to provide a corrosive solution - the cause of "black wire corrosion".

Now OK, it will take a long time before either of these events can cause critical damage, but it is notable that reports of black wire corrosion have dropped off dramatically since the introduction of peak detect chargers.

For the ultra-cautious, perhaps one overnight trickle charge for every ten peak detect charges would provide a reasonable balance (plucking figures out of thin air!).

However, as far as the OP is concerned, my advice remains to continue using his existing battery pack and charger.

--

Pete

[Andrew Cousins]

Guys Got an update for you all. I took the plunge and bought a charger that will cycle, discharge and peak charge it also has many other options.

OK some observations for you. When I charged the TX and RX batteries with the wall wart we would get four flights out of the RX pack and it would read low on the battery checker. The TX would also be down from initial reading after charge of 5.6 Volts down to 4.8 volts after four flights.

Right I put both battery pack (separately) on a 3 cycle discharge charge. Then on the morning of us going flying I done a three cycle peak charge on both battery packs.

RESULT after four flights I checked the RX battery pack and it was medium so I could have had another two flights possibly three. The TX voltage after four flights was 5.2 Volts.

Conclusion from my observations (in my situation) it seems that the £50 quid I spent on this charger has extended my flying time by at least another 30 minutes and that's a conservative estimate. NOTE the charge current I used was 300ma and the discharge was 1.5 amps for information purposes. Needles to say I am happy with my purchase.

Question. the charger at the moment can only do one battery pack at a time (in this case a four cell 4.8 Volt 2200mah pack) with the leads provided. The charger states it can do up to 15 NIMH cells. OK if I have two battery packs total 8 cells all the same voltage and capacity (2200Mah) in this case could I connect these in parallel and run the different charge discharge cycles?

Cheers All

[Geoff S]

If you want to charge 2 packs which are at a similarly discharged state then connect them in series (ie as an 8 cell pack) then it would work OK. Connecting in parallel is not considered to be the best option.

Glad you've had such good results from your new charger. It's the reason I never use simple wall-wart chargers unless there is absolutely no option. However, always be sure that, if you choose to charge through the transmitter charge port that there isn't an in built peak charge detect circuit (eg Taranis). I made that mistake on my shiny new Taranis and had to replace a burnt out surface mount MOSFET - not something I want to do again

Geoff

[Peter Christy]

Hi Andrew,

Don't read too much into the voltage readings you get on a NiMh battery! The nominal cell voltage is 1.2V, so a four cell pack would have a nominal voltage of 4.8V. Modern cells do seem to be slightly higher than this, but not by much.

Fresh off charge, a NiMh pack will read quite a bit over its nominal (4.8) voltage, but as soon as a load is placed on it, it will quickly drop to its nominal voltage. It will stay at that voltage until it is almost flat, and then drop off VERY quickly!

In other words, the voltage reading you get gives very little indication of how much charge is left!

What you need to do is *charge* it with your shiny new charger AFTER a days flying, and see how much it takes. Then compare this with the rated capacity of your battery. I doubt if you are actually using more than a quarter of you battery's capacity in the transmitter - probably a LOT less.

I have on old computer transmitter with a 1500 mAH pack in it. It is good for 10 hours of continuous operation. Most week-ends, I don't use it for more than 45 mins of continuous operation, so I have a 9 hour safety margin!!!

Receiver packs will almost certainly drain first - especially if you have lots of "digital" servos. Even older standard servos will drain more current than a transmitter, especially if you do a lot of "stick stirring".

To recap: Voltage gives very little true indication of remaining charge on NiMh cells. Do not discharge your battery after use, simply recharge it using your new charger and see how much it takes. Comparing this figure to the capacity of your pack will give a much more accurate picture of how much you've used.

One more tip: NiMh cells have a much lower "peak" to detect than older type cells. It is a good idea to charge them at a moderately high current. I charge my 2000 mAH packs at around 1 amp. This gives a reasonably rapid charge, without putting too much strain on the cells, and gives a good "peak" for the charger to detect.

Cheers,

--

Pete

[gangster]

Some interesting comments there Peter

Your final thought was good to know with regards charging nimh cells and I will bear in mind for the future. I must admit I have always tried to avoid fast charging when not necessary In that respect the wall wart Futaba charger mentioned in the op is ideal , it is, I believe a 600mA delta peak therefore probably perfect for the job.

With respect to voltage measurement in nicd or nimh battery's I suspect most modellers are confused by this, fortunately as in the case of the op who assumed that the battery was flat at 4.8 volts it does mean that they are erring on the safe side

As you said the discharge curve of ni battery's make the % readout of the Checkers totally meaningless

At least with modern fancy chargers we can actually see how much we have to put back in to get a real feel of their performance and how long we can fly

I reckon it's pretty hard to have such an amount of air time to flatten the tx or rx battery's Bacl in the good old days my mate and I had Skyleader with 500mA hr nicads one of us would buy a gallon of fuel between us on a Saturday and both flying Irvine 40 s would fly all day until the fuel was gone That's a lot of air time Never had any issue with battery issues